The present invention relates to a method for providing a coating layer of amorphous silicon carbide having a non-stoichiometric composition to the surface of various kinds of substrates or, in particular, on the surface of various kinds of materials used in the electronics.
It is well known that a coating layer of high-purity silicon carbide is excellent in the heat resistance, oxidation resistance, resistance against various chemicals and heat conductivity. In addition, silicon carbide has a characteristic as a semiconductor so that attempts are being made for providing a coating layer of silicon carbide on to the surface of various kinds of materials used in the technology of electronics such as semiconductor substrates and the like as well as various kinds of tools and vessels used in the semiconductor processing.
The method hitherto developed for providing a coating layer of silicon carbide on to the substrate surface include (1) a method in which silicon carbide is subjected to sublimation at a temperature of 2000.degree. C. or higher into vapor which is deposited and recrystallized on the surface of a substrate in the form of a coating layer (see, for example, Japanese Patent Publication No. 41-9332), (2) a method in which a gaseous mixture of a silane compound such as those expressed by the general formula (CH.sub.3).sub.n SiCl.sub.4-n, in which n is zero or a positive integer not exceeding 4, and a hydrocarbon compound such as methane is pyrolyzed at a temperature of 1600.degree. to 2000.degree. C. in contact with the substrate surface to deposit silicon carbide thereon (see, for example, Japanese Patent Publication No. 44-18575), (3) a method in which a gaseous mixture composed of a silane compound having at least one hydrogen atom directly bonded to the silicon atom such as SiH.sub.4 and a hydrocarbon compound is pyrolyzed in contact with the substrate surface to deposit the silicon carbide as the pyrolysis product on the surface (see, for example, British Patent No. 1,039,748) and (4) a method in which a mixture of silicon dioxide or elementary silicon and carbon is heated at a high temperature of 1500.degree. C. or higher (see, for example, Japanese Patent Kokai No. 52-42365).
None of these prior art methods is, however, quite satisfactory from the standpoint of practicability. For example, the first method is disadvantageous due to the use of an extremely high temperature of 2000.degree. C. or higher and cannot be applied when the substrate material cannot withstand such a high temperature. The second method is disadvantageous, in addition to the also considerably high temperature of the pyrolysis, due to the difficulty in the handling of the chlorosilane compound which is readily hydrolyzed to produce corrosive hydrogen chloride. The third method has problems that, although a coating layer of crystalline silicon carbide is obtained at a relatively low temperature of pyrolysis, an unbalance is present between the temperatures or velocities of pyrolysis of the silane compound and the hydrocarbon compound necessitating an addition of hydrogen chloride to the gaseous mixture or elaborate controlling means of the temperatures of the reactant gases. The fourth method is also disadvantageous due to the high working temperature of 1500.degree. C. or higher limiting the material of the substrate.